Community automatic exchange networks



Original Filed July'22, 1947 P. BAKKER COMMUNITY AUTOMATIC `EXCHANGE NETWORKS 14 Sheets-Sheet 2 261A/ 038| 229 24| Ans R270 r25W 253 264 mavF T lC2{5\'\ G226\\\ l, c227\ R0223 l mw PULSE v T R260 c222 @231 /zqz 0H .|L, TJ262 5\GNA| 245 m50 O VZGS 43 \252 |.MM 244 220 'l E R230 246 7 RES LR 022| V R021? Mmm Nimm RZAUPY. 'Ww-273 SIG.` I R2l5 @5f/L TANDEM 0FF|0E 30 l2 SIMP f] -PULSE R2|0 rMAGNETO OFFICE 2n f2|3 20 ToLL LNE 0|R I r VZOJ 28o l TRUNK LINE c|R. M C201 g g g I 28| NN UU swlTcHBoARD 20'0`l` TRK. L|NE CIR. 285 3,91

| @Ewen I j BOARD I ToLL oFFlcE INV'ENT0R- Pier Bakker FIG. 2

Anys.

March 24, 1953 P. BAKKER 2,632,813

COMMUNITY AUTOMATIC EXCHANGE NETWORKS March 24, 1953 P, BAKKER 2,632,813

COMMUNITY AUTOMATIC EXCHANGE NETWORKS Original Filed July 22, 194'? 14 SheetsfSheet 4 1 -6 '4'5 A\\ 446 46| 48| .4MM-337ML@ TONE C482 TOLL LINE CIR. 250 R440 454 LINEH 'I v 0483/ SEIZE TIMER 5452er MoTsTcms @3X C428 448V# cAUXTQNE sT C4|4 P-4 M TANDEM OFFICE 30 64BIT 480\ C 82T c4631 ma. 47o\ 0472i F |G. 4 INVENTOR. Pier Bakker BY Mwwqawl March 24, 1953 Original Filed July 22, 1947 P. BAKKER i 2,632,813

COMMUNITY AUTOMATIC EXCHANGE NETWORKS 14 Sheets-Sheet 5 TANDEM oFFIE 3o FIG. 5 INVENTOR.

Pier Bakker Attys.

March 24, 1953 P. BAKKER 2,632,813

' COMMUNITY AUTOMATIC EXCHANGE NETWORKS Original Filed July 22, 1947 14 Sheets-Sheet 6 RC 690 n Afiys.

March 24, 1953 P. BAKKER 2,632,813

' COMMUNITY AUTOMATIC EXCHANGE NETWORKS original Filed July 22, 1947 14fsheets-sheet'7 7 TRUNK LINE CIR 700 RING oowN SUB OFFICE 40 LINE CIR. |2802 l no March 24, 1953 P, BAKKER Y 2,632,813

COMMUNITY AUTOMATIC EXCHANGE NETWORKS Original Filed July 22, 194'? 14 Sheets-Sheet 8 ILINE E802 Waals asf/VI 854 L"N863 I MARG LSI SIMPLExI-lr -830 Lq\844 87MI f J 52 B164 1f/833 853\/\ 866A/ /L/867 www L-sgril R810 #T849 SUB OFFICE 40 @-2) TOLNE v FInder Connector Link Inc. Conn.

III

IIII IIIII F IG' 8 I -f Y INVENTOR.

Pier Bakker March 24, 1953 P, BAKKER 2,632,813

COMMUNITY AUTOMATIC EXCHANGE NETWORKS Original-Filed July 22, 194'? 14 Sheets-Sheet 9 A'rtys.

March 24, 1953 l P. BAKKER 2,632,813

COMMUNITY AUTOMATIC EXCHANGE NETWORKS Original F'iled July 22, 1947 14y Sheets-Sheet 1l c1181 c1182 91163 TANDEM OFFICE 30 1171 11907 1151/1/A LINE MME W,1152 ns1/t-V 5E imno 1123/ 112439M` N53 v 1164 TRUNK G1R. 1ooo /1156 1161175 NZL/` ff ANS TIME RLSB I w/"H Rll30 MNT-l 1113\,\v- 77,1135 c1136-\ T. st

R|l20-f FIG. Il

INVENTOR.

Pier Bakker BYv Mlmv/L March 24, 1953 P, BAKKER '2,632,9813

COMMUNITY AUTOMATIC EXCHANGE NETWORKS Original Filed July 22, 1947 1 14 Sheets-Sheet 12 SUB OFFICE 40 C|283^f Cl28 A(928| TRUNK CIR |200 1271 d' ii 125s,

,J 1262L- c1276 1263L 1272 Nia .n vlNL-J 5 i273/ mgs HOLD 1211 1V 1212 M1242 T. sT.' c123e\ $72,235' .W 2.

." HSHMPLEX- 222 R|270 L |225 1250 I V2 UPY.

F IG' I2 )Nl/ENTOR.

Pier Bakker BY n Mmqax A'Hys.

March 24, 1953- P, BAKKER 2,632,813

- COMMUNITY AUTOMATIC EXCHANGE NETWORKS Original Filed July 2.2, 1947 14 Sheets-Sheet l5 Pier Bakker Atys.

March 24, 1953 P. BAKKER i 2,632,813

COMMUNITY AUTOMATIC EXCHANGE NETWORKS 0 A INVENTOR. Pier Bakker Atys.

Patented Mar. 24, 1953 UNiifrEo :srriir-ls:s PATENT OFFICE COMMUNITYATOMATICEXCHAGE. NETWORKS Pier-Bakker, Chicago, Ill., assigner Vto Automatic Electric Laboratories, Inc., Chicago, Ill., 'ai 'cor- 'poration-Delaware Original application July 22, y1&4'7', Serial No. 762,715, now .Patent No. 2,607,854,dated August 19,1952.; Divided' una thiseppiiceticn April 6, .1950, serie-i No. 154,356

(Cuirs- 27) 1.1 Claims;

l 1' l l The" present invention relates to telephone systems and" more particularly to community auto-- matic exchange (C. A. X) networks; This ap pl'ication is a division Yof the copen'ding applicanients of the. system, whereby 'the above-outlined and additional operating` features thereof areattained..

Sect. 1.Th e generati arrangement `oy" the telephone system The invention, both as to its organization and" method of operation, together with further ob*- Zgf 1912?? Bakker, Selal NO- "763715" led 5 jects and advantages thereof, will best be undere stood by reference to the 4iollovvin s ecification In a/C' A' K .ngtwfm ttere isfreguenetlypm taken vin connection with the Iccercrnpanying tirl'denr oilice of the vfetrlliollfllit.1C` type' and a sub" 10 gram of. the area served by a telephoneA system 051C@ 01 the utomait@ P57139? whereby trame be embodying the present invention and .illustrating tween the switchboard in the' -toll `oiiice andl the the genera-l arrangement of the apparel-lus lnsubscriber 'cubeta-tions in the sub-cnice. must be eorpomted `ln several ofV the oloes thereof; and trunkeu througn the tandem oice- Also the Figs. 2` to '14, inclusive, teken together, iiiustrote tandem @ffice frequently comprises restflcd the details ci certain of the apparatus incorposervioe features preventing `some of the sube 15 ral-,ed l-n the telephone System which aoparallus Scrbevsubstatbns there'nifmm cmpleng con" has embodied therein the features of the invennections directly iso-subscriber substationsin the tion es lorlelly oulllned above Specloelly ln' Suboffle, Withu'ifthe aid @fthe wem with@ order to 'form n unified diagram, Figs. 2 to 9,

switchboard ln the toll Ofrl l l e Y .l l y inclusive, should be arranged vertically in side- Itis gif-general 0101@ 0f *he present' mvlmfm- 20 oy-,siueireiation 'from .ieft to right, and Figs. i'o

toprovldein aC. A.X.net work ofthecharaliel to 14, inclusive, should be arranged vertically described, improved swt-011mg apparatus for Sgtin 1siiie-ioy--side relation from ie'ft to right and ting: uptlie varlOuS mlectlon between: the' im* disposed respectively'below'l'igs. 5 to 9, inclusive. ferentr oiicesl m a `Slmllle alldleminem? @winner fM'ore particularly, Fig. 2 illustrates the details wlthqut sacrificing supervislon or com-pllcating 25 o'fone-of the teli ii'ne circuits incorpora-tec in tnerdirectory :lumber plain; l l Y l tiietoii cnice; Figs. 2` tc i, inclusive, iiiustrate v Another obiect of the mvenwn is t0 PrQYdG the detoiis oione of-tiie toii circuits incorporate-ri in a telephoneV sifste'rinofV the WD@ noted.. 2in im* in the 'tandem office; Figs. 5 and e illustrate the proved trunk selector-digit- Sender and repeater*- de'tails ci therepeater and trunk selector incortliunk Selector aff'ang'ement in which rst'auto 30 porated in the tandem oce' Figs 10 and l1 matic switching apparatus iS TGSDODSV@ t0 a given illustrate the ldetails of one oithe trunk circuits dgitto select either the repeater-trunk selector incorporated in the tand-em omce- Figs. 7 to 9 or Avthe trunk selector-digli; Sender dependmg inclusive, illustrate the details of a trunk circuit upon trail-lc condltlOnS whereupon the Selected incorporated in the sub-office' Figs 12 and 13 Vrep'etiter-trunk selector selects an idle trunk .line 35 illustrate elle details of one Ofa ,gro'u of trunk extending to the desired destination, or the olloults incorporated ln the sulommoel? and Fr selected trunk Selector-digit. Sender Selects an iriliiiustrates the-details oi e trunk seicct '1go idle trunk extending t0 Second automatic SWitChdigit Asruiri'er 'incorporated in the sut-unicrean ing` apparatus ami Jthen operates the 'Second Referring new more perticuiuriy to Fis. 1 ltrie sw1tch1ng apparatus '150 select 'an-1d1e trunk line 4o telephone vsystem there illustrated serves anlarea extending to the desiredl destination. comprising a toll office lil, al magneto oice 20 riV further object of the invention is toorOVid a tandem l'oiiice all and a sub-cnice 40 the toll in a: trunk circuit, including two .incoming trunks; office. I0 being disposed 'relatively remote from an. improved arrangement whereby a tone test the tandem office 3l), and the tandem" oiiice 3l) is :perfrmed When 011e 01 the inCOm-ng trunks 45 being disposed relatively near to the magneto is employed; and a' reverse battery control is perocez `and tothe sub-oliceY lll). The toll oice formed when the @ther of the incoming trunks Ill serves subscriber `substations of any suitable is)enmloyed`A` typev and comprises a manual dial switchboard AFurther featuresofithe invention Vpertain to 20B; while the' magneto oflice 20 serves subthe yparticular arrangement of. the circuit ele 50 scriloerA substations of the magneto type and comprisesa manual dial switchboard 236. The' tandem. ofllce'isa relatively small oiiice of the automatic. ,typen serving a. Anumber of diierent groups of subscriber substations rendered diiierent classes of service and at least one group of paystations. One of the groups of subscriber substations includes the subscriber substation Tl. Also, the sub-oice 80 is a relatively small oiiice of the automatic type serving a group of subscriber substations, including the subscriber substation T2.

The toll oice l Iand the tandem oce 30 are interconnected by a small group of toll lines; which group may comprise three individual toll lines, including the toll line 220. The magneto office and the tandem oiiice 30 are interconnected by a small group of trunk lines; which group may comprise three individual trunk lines, including the trunk line 280. 'I'he tandem office 30 and the sub-oiiice 40 are interconnected by a single trunk line 600; and also by a small group of trunks; which group may comprise two individual trunks, including the trunk H90. Each of the toll lines 220, etc., terminates in toll line circuits respectively disposed in the toll oilce I0 and in the tandem oflice 30, the toll line 220 terminating in the toll line circuits 2|0 and 250 respectively disposed in the toll oiilce |0 and in the tandem oiiice 30. Each of the trunk lines 280, etc., terminates in trunk line circuits respectively disposed in the magneto office 20 and in the tandem oice 30, the trunk line 280 terminating in the trunk line circuits 285 and 28| respectively disposed in the magneto oice 20 and in the tandem oiiice 30. The trunk line 600 .terminates in a repeater .and trunk selector 500 disposed in the tandem oiiice 30 and in a trunk line circuit 100 disposed in the sub-office 40. Finally, each of the trunks H80, etc., terminates in trunk circuits respectively disposed in the tandem oce 30 and in the sub-office 40, the trunk H90 terminating in the trunk circuits |000 and |200 respectively disposed in the tandem oiiice 30 and in the sub-cnice 40. In the toll cnice I0, each of the toll line circuits 2|0, etc., is accessible to the switchboard 200; and in the magneto oiice 20, each of the trunk line circuits '285, etc., is accessible to the switchboard 285.

'Ihe tandem oiice 30 also comprises autothe trunk line circuit 28| being provided with the incoming trunk 30|. Also the repeater and trunk selector 500 is provided with an incoming trunk 90; and each of the trunk circuits |000, etc., is provided With an incoming trunk, the trunk circuit |000 being provided with the incoming trunk 400. The incoming trunks 480, etc., extending to the toll line circuits 250, etc., are accessible to the repeater and trunk selector 500 and to the two incoming connectors 300, etc.; while the trunks 410,' etc., extending to the toll line circuits 250. etc., are accessible to the connectors of the various links 380, etc. The incoming trunks 39|, etc.extending to the )trunk line circuits 28|, etc. are accessible both to the connectors of the links 390, etc., and to the two incoming .connectors 300, etc. The various subscriber lines 385, etc., are accessible to the connectors of the various links 380,

etc., and to the two incoming connectors 300, etc.

matic switching apparatus including a plurality i of lnder-connector links 300, etc., provided withA an associated distributor 388, and two incoming connectors 300, etc., respectively individually associated with the trunk circuits |000 etc., the trunk circuit |000 being connected to the individually associated incoming connector 300 by a trunk H80. Each toll line circuit 250, etc., is provided with a line circuit individual thereto, the toll line circuit 250 being provided with the line circuit 384 individually connected thereto by the trunk 380. Also each trunk line .circuit 28|, etc., is provided with a line circuit individual thereto, the trunk line circuit 28| being provided with the line circuit 385 individually connected thereto by the trunk 283. Finally, each subscriber substation is provided with a line circuit individual thereto connected to the associated subscriber line, the subscriber substation T| being provided with the line circuit 381 individually connected to the associated subscriber line 386. The various line circuits 384, 385, 381, etc., lare respectively connected to the distributor 388 and are accessible to the nders of the various links 390, etc. Each rtoll line circuit 250, etc., is provided with two incoming trunks, the toll line circuit 250 being provided with the two incoming trunks 410 and 480 and each trunk line circuit 28|, etc., is `provided with an incoming trunk,

The incoming trunk 880 extending to the repeater and trunk selector 500 is laccessible to the connectors of the various links`390, etc.; while the incoming trunks 400, etc., extending to the trunk circuits |000, etc. are accessible to the connectors of the various links 390, etc.

The sub-oice 40 comprises automatic switching apparatus, including a plurality of iinderconnector links 880, etc., provided With an associated distributor 883; and an incoming connector 885 individually associated with the trunk line circuit '|00 and connected thereto by the trunk 800. Each trunk circuit |200, etc., is provided with a line circuit individual thereto, the trunk circuit |200 being provided with the line circuit T10 individually connected thereto by the the incoming trunk |380; and the trunk line circuit '|00 is provided with an incoming trunk 910. Also the sub-office comprises a trunk selector and digit sender |400 provided with an incoming trunk 898. The incoming trunks |380, 910, 890, etc., are accessible to the connectors of the various links 884, etc.; while the trunk selector land digit sender |400 has access to the incoming trunks |380, etc., extending `to the trunk circuits |200, etc. Finally both the connectors of the various links 888, etc., and the incoming connector 885 'have access to the various subscriber lines 88|, etc.

Sect. 2.-The apparatus incorporated in the telephone system In the toll oiice I0, the switchboard 200 is of the conventional manual dial type, including cord circuits, not shown. Each of the toll line circuits is identical to the toll line circuit 2 0; which comprises, as shown in Fig. 2, a relay group including a simplex pulse relay R2|0 and a signal relay R2 5, as well as a repeating coil RC2 I 1.

In the magneto oflice 20, the switchboard 286 is of the conventional manual dial type and may be identical to the switchboard 200. Similarly, the

trunk line circuits 285,`etc., may be identical to the toll line circuit 2 I0.

In the tandem oiiice, the toll line circ ts 250,-'-

etc., and the trunk line circuits 28|, etc., may be identical; the toll line circuit 250 comprises, as shown` in Figs. 2, 3 and'4, a repeating coil RC223, ar timer 4125, and a relaygroup including a signal relay R230, a supervisory relay R240, ,a dial relay R250, a pulse relay R200, an answer relay R21-0, a switch relay R310, a control relay R320, a liner relay R330, a time release rel-ay R340, two

*hold relays R350 and R300, a time release relay R310, a line relay R410, a timer relay R420, a seize relay R430, a tone relay R440, two start relaysR445 and R450 and a reverse battery relay R400.

'Therepea'ter andl trunk selector 500 comprises, as shown in Figs. 5 and 6, -a repeating coil RC99`0 and a relay group including three select relays R510, `R520 and R530., a reverse battery relay R540; avbusy relay R550, a test relay R560, a release relay R510, a control relay R500, a line relay R590, a hold relay R610, a dial relay R020, a cut-'o relay R530, an answer relay R640, asupervisory relay R050, a start select relay R055, a simplex relay R060', a ring-down relay R005 and two start relays R010 and R500.

l The trunk circuits |000, etc., are identical; and the trunk circuit |00 comprises, as shown in Figs. and 11, a Vrepeating coil RCI115, a timer, not showin, and a relay group including a reverse 'batteryrelay vR1010,1a cut-off relay R1020, a timer relay R1030, a seize relay R1040, a control relay R1050, a Adial relay R1`060, a hold relay R1010, two line relays R1000 and R1 1 10, a supervisory relay R11 20, a time release relay R1 130, an answer relay R'I140, a switch relay R1 |50, a hold relay R1 |00, anda simplex relay R1 |10.

Also, in the tandem oice 30, the line circuits 384-, 385 and 301 may be of any suitable types, while the distributor 385 is of any conventional type. The subscriber substations T1, etc., are provided with conventional substation equipment; and the paysta'tions, not shown, are of the conventionalprep'ayrnent type. Further, the private subscriber lines are provided with call registers andl meters, not shown. Finally, the lnder-connector links 390, etc., .are of the Strowger re stricted service type disclosed in the co-pending application of Pier Bakker, Serial No. 723,525, filed January 22, 1947; while each of the incoming connectors 300, etc., is of the Strowger type andi is substantially identical to the connector portion of the link 390. In passing, it is noted that'the link 390 is of the mixed service type and isresponsive to the single digits '1, 8, 9 and 0, re spectively, to select the groups of trunks termina'tedv inV the first, second, third and fourth levels thereof and then automatically to operate in order lto select an idle trunk in the previously selected group or level. Also the link 390 is responsive to the prex digits 2 or 3 followed by one of the digits 5, 6, '1, 8 and 9 tov select the respectively corresponding fth, sixth, seventh, eighth and ninth levels thereof, terminating the lines extending to the subscriber substations and paystations. Thereafter, the link 390 is responsive to any'third digit from 1 to l0 to select the respectively corresponding line in the previously selected level. Finally, `the finder-connector link 390iis responsive to any fourth Vdigit from 1 to 0 to'bring about code ringing of the selected line in the event it is idle. The combination of the first o'r prefix digit and the fourth code digit permits the link 390 tc ring the called line with any one: of twenty individual codes; whereby as many asg'twenty party vsubscriber substations may be arranged-onanysingle partyfline. ,f l

Also-'thelink 390 comprises a restricted' serviceA arrangement, whereby certain of the subscriber lines may not extend connections via the two groups of trunks that are respectively selected in i response to -dialing the digits 7 and 9; and none of the subscriber lines may extend connections via the trunks that are selected iriresponseA to dialing the `digit 8.

In the sub-office 40, the trunk line circuit 100.

comprises, -as shown in Figs. 7, 8 and 9, a .repeating coil RC'10`0, a timer 936 and a relay group including twoV ring-down relays R and R120, a.

switch relay R130, a line relay R140, an answer relay R150, a hold relay R810, a simplex relay R020, a hold relay R830, a time release relayR840,`

a dial relay R850, a control relay R860, a `line `relay RI010, a tone relay R910, a seize relay R920, two start relays R930 and R040, a timer relay R950 and a reverse battery relay R960.

Also, the trunk circuits '11200, etc., are identitical to the trunk circuit 1000; the trunk circuit 1200 comprising, as shown in Figs. 12 and 13,21.

repeating coil RC1r215, a timer, not shown, and a relay grou-p including a reverse battery relay R1310, a cut-oile relayYRI320, a timer relayR1330,

a seize relay H1300, a control relay R1'350, a dial relay R1350, a hold `relay R1310, two line relays 10.1300 and R1210, a supervisory relay R1l2`20, a time release relay R1230, an answer relay H1240, a switch relay R1250, a hold relay Rf1260 and a simplex relay R11210.

Also in the sub-office 40, the line circuitsA 1.10, 002, etc., may be of any suitable types; while the distributor 003 is of Vany conventional type. The subscriber substations '-DZ, etc., are provided with conventional substation equipment; while links 304, etc., and the incoming connect-or 085, are of the conventional Strowger types.

Finally, the trunk selector and -digit sender 1400 comprises, as shown in Fig. 14, a relay group including two select relays R|4|0 and R'14Z0, a busy relay R|=430, a test relay R1440,

a cut-off relay H1450, three pulse relays R1485- R1445, and R1400, a shunt relay R14'10, `a line relay R1415, a control relay H1480, and a start relay E1000. Also, the trunk selector and digit sender 1400 comprises a send switch 1401 of the rotary type, including two wipers 11402 and |403 providedv with a magnet M1|40|4 for `driving the wip-ers noted step-by-step in the clockwise direction away from their home positions with respectV to the associated contact banks.

A better understanding of the connection and arrangement of the apparatus Aincorpor'tecl in the telephone system will be facilitated from a considerationoi thev extension of'calls involving the various offices.

Sec. 3.'-Local calls in the tandem office First assuming that a call is initiated at the' subscriber substation T1 in the tandem oice 30 that is to be completed locally to another subscriber substation therein, the line circuit 3'81 is controlled via the subscriber line 301i in order to govern ope-ration of the distributor 388;

whereby an idle yone of the links, such, for eX" ample, as the link 300 is assigned' thereby. The

nder of the assign-ed link 390 operates to find the subscriber line 306 exten-ding to the calling subscriber substation 'Ill whereby the line cir-- cuit 301 is operated in order to mark the subscriber line 300 as busy to the other links 390, etc, Also the connector of thelink 3'90 operates to return dial ton-e over the subscriber line 381i to the 4callin-g subscriber substation T1; wherebythe' subscriber at the calling subscriber substation TI proceeds to dial the directory number of the called subscriber substation, which number Vmight be 3654. The iirst digit 3 received by the link 330 indicates that the pres-ent call is a local call and selects a po-rtion of the ringing code. The connector of the link 390 responds to the second digit 6 to select the corresponding sixth level; Iand then responds to the third digit to select the correspon-ding fifth line in the previously selected level; which line extends to the called subscriber substation. The connector of the link 390 then responds to the fourth digit 4 to select the remainder of the ring-ing code that is to be employed to ring the called subscriber line. .The first or prefix digit 3, in conjunction with the fourth digit 4, selects one of twenty ringing codes at this time; whereby the particular selected ringing code is projected over the called subscriber line in order to signal the corresponding one of the twenty party subscriber substations connected to the called subscriber line, assuming the called subscriber line is of the twenty party type and provided it is idle at this time. The operation of the connector of the link 390 to return busy tone current to the calling subscriber substation TI in the event the called subscriber line is busy is in accordance with conventional practice; and the remainder of the operation of the connector of the link 330 in response to the answering of the cal-l on the called subscriber line, as well as the subsequent release of the established connection, are in accordance with conventional practice.

In view vof the foregoing, it will be understood that a call from a subscriber substation in the tandem exchange may be completed locally to a paystation therein in an identical manner. Also, it will be understood that a call may be initiated at a paystation in the tandem exchange 30 by depositing a coin or check thereat and then subsequently completed locally to a called subs-cri-ber substation or paystation therein in a conventional manner.

Sect. 4.--A call fromV a subscriber substation m a paystation in the tandem oice to a subscriber substation in the sub-oice First assuming that a call is to be extended from a subscriber substation, such, `for example, as the subscriber substation TI in the tandem oiiifce 30 to a called subscriber substation, such, for example, as the subscriber substation T2 in the sub-oiiice 40, .the subscriber at the calling subscriber substation TI first initiates the call whereby the link 390 may be taken for use in the manner previously explained. The subscriber at the calling subscriber substation TI then dials the prefix digit 9 followed by the directory number. of the called subscriber substation T2; which number might be 23; whereby 9-23 may be dialed. The connector ofV the link V39|) responds to the digit 9 to select the` corresponding third level and then an idle trunk-terminated therein, such, for example, as the trunk 400 extending to the trunk circuit i000, the trunk 400 being marked as idle to the connector of the link 3.90 by the absence of ground potenti-al upon the control conductor C403 thereof. When the connector of the link 390 seizes the trunk t, a loop circuit is completed for energizing in series the windings of the line relays RI08 and RI I I0 in the trunk circuit |000; this loop circuit extending from ground potential by way of the winding of the line relay H1080, the contacts ||54, the lower lett-hand winding of the repeating coil RC|I|1I5 and the contacts |0I4 to the line conductor C402 of the trunk 400, and from battery :potential by =way oi the iwinding of the line relay RI |I| 0, the contacts |52, the upper lett-hand wind-ing of the repeating coil RCI'I15 and the contacts |0I2 Ito the line `conductor OMI of the trunk 1400. At this time the line conductors 040| and C402 of the trunk E400 are connected together by w-ay of the link `lSIt and the subscriber line 3816 at the calling subscriber substation TI. When `this loop circuit is thus completed, both of fthe Iline relays Rlt and RI I I0 operate. Upon operating, the line relay RII I0 completes, at the contacts III I I, a circuit for operating the hold relay RI010. Upon operating, the hold relay RI010 completes at the contacts |013, a path, including the contacts I I|3, tor applying battery potential by way of the winding of the supervisory relay R||20 to the simplex conductor OI |16; which simplex conductor CI |116 is Iconnected Iby way of the upper fand lower lright-hand lwindings of the repeating coil IRCIHB, the line conductors of the trunk H `and the upper an-d lower left-hand windings of the repeating coil RC |215 to lthe simplex conductor rCI=21 |5; which simplex conductor CI1215 `is connected |by way of the contacts |I31I and |353 Iand the rwinding of the simplex relay RI2=10 in the trunk ycircuit l|200 to ground potential. Accordingly, at this time the lwinding of the supervisory relay 'RI'II20 in the Itrun-k circuit |030 is energized 'in series with the winding of the simplex relay R. I 210 in the trunk `circuit 1200; whereby both the supervisory relay RI |20 and the simplex relay RI21f0 operate. IAlso upon operating, the 'hold relay R|010 in the trunk circuit |0|l0 completes, at the contacts 'I01 2, a circuit, including the contacts |034, for operating Athe time release relay RIII30. Upon operating, the time release relay RI |35? completes, at the contacts H34, a path for applying ground potential Ito Ithe control conductor `C4|3 of the 'trunk 400, thereby to mark the trunk l40|] as busy to the other llinks 390 etc., having access thereto. Also the time release relay RI I3@ completes, at the contacts I |35, a path for applying ground potential to the timer start conductor CI |38 in order to initiate operation of the associated timer, not shown. Further the time release relay RII30 completes, at the contacts 'I |31, a path, including the contacts |012| and |032, for applying battery potential -by way of the winding of the timer relay R|030 Ito the timer tconductor 'C|024; however, lthe 'timer relay R|030 is not operated at this time.

Upon operating the simplex relay RI 210 in the trunk circuit |200 completesat the contacts |213, a circuit lor operating @the hold relay RI-2'60. Upon operating, the hold relay H1260 completes, at the contacts |262, a circuit Afor operating rthe switch relay RI2l50 "and a multiple circuit for energizing the lower winding of the answer relay RI'240. When Ithe lower winding of the yanswer relay RI2-40 is thus energized, it ldoes not operate at this time. Upon operating the switch relay R.I-250 interrupts, at the contacts |:252 and |254, normal Iconnections between the windings of ythe line relays RIZ I0 `and R|380 and the upper right-hand winding and the lower righthand winding, respectively, of the repeating coil' RCI21'5; and completes, at the contacts |25l, |253, yI2 525 and |2516, ia path, including 'the resistor |12 Eiland 'the upper rightehand winding and the lower right-hand Winding of the repeating coil `the latter relay operates.

9 REIMS, for the upper ivrindin'g yof A*the answer relay Rf|2|40 across the line conductorsV lc lf2-sl and oleic of the tmnk `s zen extending to thefline-'circuit 110. Further, lthe switch relay H1250 completes, at the contacts 4.250, ia path, in-

cluding the contacts |233, for applying ground potential to the control conductor Cl'30'3 of lthe trunk 4380, thereby 'to mark the trunk |380 las busy'to the various links 884, etc., having access thereto.

When 'the upper winding of the answer relay H1240 is thus bridged across the lin-e conductors C|248r| and IC0202 or the trunk |280, it is energized, but it is not poled to operate. Also, the line circuit 110 operates Ito control 'the distributor l003; whereby ,fan idle one of the .finder-connector links, such ior example, was the link 000 is assigned for use at this time. The finder of .the lin-.k 804 finds the lcalling'trunk |280 marked lby the .line circuit 110; whereby' the connector of the link''sis .conditioned to be responsive to digitsrec'eivedover thetrunk |280.

When `the subscriber at the calling subscriber substation. TI dials the firstdigit L2 of the direcftcry ,number o'f the called subscriber substation T2, the line relays Rl 000 and YRi in the trunk circuit |000 follows. Each time the line relay Rl H0 .restores 'and then reoperates, it interrupts and then recompletes, at the contacts the previously'mentioned circuit for maintaining operated the hold relay R|010; whereby the latter relay remains operated during impulsing as it is .of the slow-to-release type. 4Also each time the line relay RI |0 .restores and then reoperates, it completes vand then interrupts, at the `contacts .|||2, a circuit, including the contacts |022 and |32, for operating the dial relay Rl 000; whereby the latter relay operates and remains operated vduring impulsing as it is of the sloW-to-release type. Upon operating, the 'dial relay Ri-00 cornple'tes, at the contacts |053, a path, including the contacts |01|, for connecting the resistor |025 in shunt to the winding of the line relay R|030 in order to improve impulsing over the loop circuit extending back to the calling subscriber substation T|. Also the dial relay Rt|000 completes, at the contacts |055, a path, including the contacts ||36', forconnecting the resistor H25 in shunt to the winding of the supervisory relay R||20 in order to improve impulsing over the simplex ccnductor Cl |15. Also each time the line relay RH l0 restores and then reoperates, it interrupts and then recoinpletes, at the contacts Hit, the previously traced circuit for energizing in series the winding of the supervisory relay R! 20 in the Vtrunk circuit |000 and the winding of the simplexrelay RA 210 in the trunk circuit |200 whereby the relays mentioned follow; followed by the supervisory relay Ril |20 in the trunk circuit |000 being Without effect.

The rst time the simplex relay R|210 in the trunk circuit |200 restores'and then reoperates, it

completes and then interrupts, lat the contacts |212, a circuit, including'the contacts |200, |263 and |343, for energizing in series the upper and lower windings of the seize relay RlSdll; whereby Upon operating the seize relay R|340 completes, at the contacts |342, a holding circuit, including the contacts |258 and the grounded control conductors C1203 of the trunk |280, for energizing in series the upper and lower windings thereof. Also each timev the sirnplex relay R|210 restores and then reoperates, it

interrupts and then recompletes at the contacts |213, the vpreviously mentioned circuit for maintaining operated the hold relay H4260; whereby thelatter relay remains operated during impulsing as it isof the slow--to-release type. Also, each time the simplex relay -RI210 restores and then reoperates, it completes and then interrupts, at the contacts |212, a circuit, including the contacts |264 and |24|for operating the dial relay R|300; `whereby the latter relay operates and remains operated duri-ng impulsing as it is of the sloW-to-release type. Upon operating the dial relay R|360 completes, at the contacts |3B|, a path, including the resistor |223 and the contacts |26I, |21| and |25l, across the line conductors C|20| and Cl282 of the trunk |200; thereby to improve impulsing over the trunk |280 and the line circuit to the connector of the link 884. Finally, each `time the simplex relay R|210 restores andthenireoperates, it interrupts and then recompletes, at the `contacts |21|, the previously traced path across the line conductors vC|28| and C1202 of the trunk |280; whereby the impulses of the second digit 2 are transmitted over the trunk |200 and the line circuit 110 to the connector of the link 804 in order to eifect corresponding operation thereof.

At the conclusion of the second digit 2 dialed at the calling subscriber substation Tl, the line relays R|080 and RI l0 in the trunk circuit |000 remain operated; whereby the hold rel-ay R|010 is retained in its operated position and shortly thereafter the dial relay R|060 restores. Upon restoring 'the dial relay R|060 removes the resistors |025 and H25 from across the winding of the line relay R|030 and the winding of the supervisory relay R||20, respectively. Also `at `this time the winding of the supervisory relay RI |20 in the trunk circuit |000 and the Winding of the simplex relay R|210 in the trunk circuit l2 00 are steadily energized in series circuit relation; whereby the relays mentioned are retainedv in their operated positions.

The operated simplex relay IRI-2.10 in the trunk circuit |200 retains operated the hold relay RI260 and effects restoration of the dial relay R|360 shortly thereafter, since the latter relay is of the slow-to-release type. Upon restoring the dial relay Rl|300 interrupts, at the contacts |36|, the previously traced path for connecting the resistor |223 across the line conductors Cl28l and C1282 of the trunk |200; whereby the upper winding of the answerv relay R||240 is no longer short-circuited `by the resistor |223. Also upon restoring, the dial relay R|360 completes, at the contacts |30fl, a holding circuit, including the contacts |342, |34l, |251 and |202, for energizing in series the upper and lower windings of the seize relay Rl340; and a multiple path, also including the contacts |258', for applying ground potential in 'the vtrunk circuit |200 to the control conductor C|203 of the trunk |280, thereby to retain operated the link 084. Y

In view of the foregoing explanation of the kmanner in which the second digit 2 dialed at the calling subscriber substation Tl is received by the trunk circuit |000 and repeated therefrom over the trunk |00 to the trunk circuit |200 and then repeated therefrom to the connector of the link 88s, it will be understood that the third digit 3 dialed at the calling subscriber substation TI is transmitted in an identical manner to the connector of the link 384. The connector o-f the link 084 responds to the digits 2 and 3 to select the subscriber line 88| extending to the called subscriber substation T2. The subsequent operation of the connector of the ling 884 depends upon the idle or busy condition of the called subscriber substation T2 at this time; and in the event the called subscriber substation T2 is busy at this time, the connector ofthe link 084 operates in order to return busy tone current over the trunk |230 to the trunk circuit |200; which busy tone current traversing the upper right-hand winding and the lower right-hand winding of the repeating' coil RC|2`|5 induces a corresponding busy tone current in the left-hand windings thereof. The busy tone current is returned over the trunk H90 and traversing the right-hand windings of the repeating coil RCI induces a corresponding busy tone current in the upper left-hand winding and the lower left-hand winding thereof; which busy tone current is returned over the loop circuitto the calling subscriber substation TI in order to indicate to the subscriber thereat that the desired connection cannot be had at this time by virtue of the busy condition of the called subscriber subst-ation T2.

On the other hand, in the event the called subscriber substation T2 is idle at this time, ringing current is projected from the connector of the link 884 over the subscriber line 80| thereto and the line circuit 882 is operated in order to mark the subscriber line 08| as busy to the other links 884, etc., having access thereto. Also, ringback tone current is returned from the connector of the link 884 over the previously traced connection to the calling subscriber substation TI in order to indicate to the subscriber thereat that the called subscriber substation T2 isrbeing rung.

When the subscriber at the called subscriber substation T2 answers the call, the connector of the link 884 operates in order to reverse the polarity of the trunk |230; whereby the upper winding of the answer relay RI 240 is poled to operate. Upon operating, the answer relay R|240 completes, at the contacts |242, a circuit for energizing the upper winding of the control relay RISSII; whereby the latter relay operates. Upon operating the control relay R|350 completes, at the contacts |354 a holding circuit, including the contacts |222 and |250 and the resistor |225, for energizing the winding of the simplex relay Rl2l0; interrupts, at the contacts |353, the previously traced original path for connecting ground potential by way of the winding of the simplex relay R|2`|0 to the simplex conductor C|2'|5; and completes, at the contacts |352, a path, including the contacts |314 for connecting battery potential by way of the winding of the supervisory relay R|220 to the simplex conductor CIZ'IG. Accordingly, at this time the winding of the supervisory relay R|220 in the trunk circuit |200 is short-circuited in series with the winding of the supervisory relay RI| in the trunk circuit |000; whereby the supervisory relay R|220 is retained in its restored position and the supervisory relay R||20 restores.

Upon restoring, the supervisory relay R||20 in the trunk circuit |000 completes, at the contacts ||2|, a circuit, including the contacts |01 I, |062 and ||3l, for energizing the winding of the cut-oit relay R|020, and a multiple circuit, also including the contacts |08I, for energizing the winding of the reverse battery relay RIOI0; whereby the cut-off relay R|020 and the reverse battery relay Rilll operate shortly thereafter. both of these relays being of the slow-to-operate type. Upon operating, the cut-ofi relay R|020 interrupts, at the contacts |02I, the previously traced connection between the winding of the timer relay R|ll30 and the timer conductor C I 024,

thereby positively to prevent operation of the timer relay RI030 under the control of the associated timer, not shown. Upon operating, the reverse battery relay RIOI0 completes, at the contacts |0I5, a holding circuit for energizing the winding thereof, and including the contacts ||3I, ||2|, |052 and IIl'II. Also the reverse battery relay RIO|0 reverses, at the contacts I 0I|, |0|2, I0|3 and I0|4, the polarity of the trunk 400 with respect to the line relays RI080 and RI I I0; which reversal of polarity over the trunk 400 and the link 390 is eiective to operate a meter, not shown, individually associated with the calling subscriber substation TI or otherwise to assess a charge against the calling subscriber substation TI is completed between the calling subscriber substation TI in the tandem office 30 and the called subscriber substation T2 in the sub-office 40.

At the conclusion of the established connection, when the subscriber at the called subscriber substation T2 disconnects, the connector of the link 884 isoperated in order again to reverse the polarity of the trunk |280; whereby the answer relay RI240 in the trunk circuit |200 is poled to restore. Upon restoring, the answer relay R|240 interrupts, at the contacts I 242, the previously mentioned circuit for energizing the upper winding of the control relay RI350, thereby to cause the latter relay to restore. Upon restoring, the control relay R|350 interrupts, at the contacts |352, the previously traced path for connecting battery potential by way of the Winding of the supervisory relay R|220 to the simplex conductor CIZ'IS; interrupts, at the contacts` |354, the previously traced holding circuit for maintaining operated the simplex relay RI2'I0; and recompletes, at the contacts |353, the previously traced original path for applying ground potential by way of the winding of the simplex relay R|210 to the simplex conductor CI2I6. Accordingly, at this time, the winding of the simplex relay RI2'I0 in the trunk circuit |200 is again energized in series with the winding or the supervisory relay R||20 in the trunk circuit |000; whereby the simplex relay R|2`|Il is retained in its operated position and the supervisory relay RI |20 reoperates. Upon reoperating, the supervisory relay RI |20 interrupts, at the contacts ||2|, the previously traced circuits for maintaining operated the cut-off relay R|020 and the reverse battery relay R|0|0. Upon restoring, the reverse battery relay RIO|0 again reverses, at the contacts |0|I, |0I2, |0|3 and |0|4, the polarity of the trunk 400 with respect to the line relays RI 080 and RI |I0 in the trunk circuit |000; however, without eiect at this time. Upon restoring, the cut-ofi relay R|020 again completes, at the contacts |02I, the previously traced connection between the winding of the timer relay R|030 and the timer conductor C|024 extending to the timer, not shown; whereby operation of the timer is again rendered eiective.

When the subscriber at the calling subscriber substation TI disconnects, the loop circuit extending to the line relays R|080 and RII I0 in the trunk circuit V|000 is interrupted; whereby the relays mentioned restore. Upon restoring, the line relay RI I I0 interrupts, at the contacts IIII, the previously mentioned circuit for maintaining operated the hold relay RIU'ID; whereby the latter relay restores shortly thereafter, it being of the slow-to-release type. Upon restoring the hold relay R|010 interrupts, at the contacts |012, the previously traced circuit for At this time an established connection. 

